[nullindividual]

I wouldn’t think that would be appropriate for Ethernet due to cross talk.

[wmf]

Four-lane and eight-lane twinax cables exist; I think each pair is individually shielded. Beyond that there's fiber.

[pezezin]

Those cables definitely exist for Ethernet, and regarding cross talk, that's what shielding is for.

Although not for 200 Gbps, at that rate you either use big twinax DACs, or go to fibre.